Ellipsograph



P. F. DUBOIS April 16, 1935.

ELLIPSOGRAPH Filed June 18, 1934 MTN e5 5 E5 1 INVENTOR f u-urrso sraresearner orrics ELLIPSOGRAPH Peter F. Dubois, Detroit, Mich. ApplicationJune 18, 1934, Serial No. 731,124

3 Claims.

My invention relates to ellipsographs, and its principal object is toprovide an apparatus which can be easily and quickly adjusted todescribe e1- lipses of any desired size from the largest for 5 which theapparatus is designed down to the smallest which would be of anypractical use, as

well as ellipses having any desired proportion between the major andminor axes within the predetermined range, of the apparatus.

Ellipsographs of the type at present in use consist in general of a pairof trackways arranged in right angle relation and a pair of trammelshaving two adjustable heads adapted to engage the said traclrways and athird head for holding a pencil or other instrument by which the desiredcurve is marked or impressed-upon paper or other material.

a sheet of Such devices have the inherent disadvantage that thetrackways extend to a certain distance in the path of the markinginstrume it is impossible to describe ellipses of nt so that very smalldimensions, and further, the movable trammels possess very littlestability, so that even with the greatest care in operation the accuracyof the curve produced is indifferent.

According to the present invention I have provided a unitary,self-contained structure in which.

therange of the instrument.

With these and other objects in View, the in vention consists in theimproved construction, ar-

rangement, and combination of parts which will be hereinafter fullydescribed, reference being had to the accompanying drawing, in whichdrawing Figure 1 is a plan view.

Figure 2 is a section on line 2-2 of Figure 1.

Figure 3 is a fragmentary section on line 33 of Figure 1, enlarged, and

Figure 4 is a fragmentary section on line 44 of Figure 1, enlarged.

Like characters designate corresponding parts throughout the severalviews.

I is the base, of celluloid or other suitable material, adapted to restupon the surface of a drawing table or other support, and 2 plate ofcelluloid arranged in parallel lation with the base and connected studs3 or other means. The base I is is a cover spaced rethereto bypreferably of rectangular shape, as shown, and is provided with aworking edge 4 which forms part of the generating mechanism of thedevice.

Between the base i and the cover 2 is a spacer 5 which consists of afiat plate of celluloid or other suitable material cut away at El toprovide clearance for the movable element or scriber f: by which thedesired ellipse is generated. The member s consists essentially of arectangular plate of celluloid or other material of such thickness as tobe capable of moving freely between the base plate I and the cover 2 andis provided with a slot 1 adapted to receive a pair of fulcrum pins 8,9, one edge of the said slot being graduated in inches or fractionsthereof or in any suitable manner adapted to facilitate adjustment ofthe fulcrums to produce the desired result. In the member 5, and inalignment with the slot 7 are a pair of openings it, E i adapted toreceive a stylus, pencil or other marking instrument by which theellipse is to be impressed upon the paper or other desired surface.

threaded member 8% having a flange 82 adapted to slide within a recessin the other side of the member 6. Below the flange 82 is a projection83 adapted to engage the working edge 4 of the base plate while upon theupper threaded portion 8! is screwed a nut 34 of elongated form whichserves as a handle for the operator. The fulcrum 5 is of similarconstruction to the fulcrum 8, having the screw threaded member 95,

flange '92, and handle 9d, but in this case there is no projection belowthe flange as. The handle 9 is provided with a journaled portion whichis rotatably mounted in a bearing l2i formed in the sliding member 12,the said member being adapted to slide back and forth within a slot 22in the cover plate 2. Projecting upwardly from the member i2 is a pinI22 with which engages a resilient band of rubber or other suitablematerial 13 which is in general of triangular shape, as shown in Figure1, the apices I3l, I32 of which engage in slots 23, 24 in the coverplate.

It will be observed from the foregoing description and by reference tothe drawing that, when the parts are in the relative position shown inFigure 1 and the pencil or stylus is inserted into the opening l0,movement of the stylus in the direction indicated by the arrow M willcause the same to describe an ellipse having major and minor axesdependent upon the relative positions of the fulcrums 8 and 9 and theopening Ill. ing this movement, the member l2 will be drawn inwards bythe resilient member 53 until the slot 7 comes into alignment with theslot 22, the memher 6 being then in the position shown in broken linesat 63 in Figure 1, after which the slide will The fulcrum 8 consistsessentially of a screw Dur- Cir

be withdrawn against the action of the member I3 until the member 6arrives at the position shown in broken lines at 64 in Figure 1. Duringthese movements the projection 83 is maintained at all times in slidingcontact with the working edge 4 upon the base, as a result of which thepencil will have described one-half of the desired ellipse upon themajor axis :r--:z: which is marked upon the surface at the commencementof the operation.

The apparatus is then turned around through 180 degrees and the workingedge A is re-aligned with the axis r:c while at the same time thefulcrum Q is ali ned with the minor axis y- 7J, this being facilitatedby the centerline H23 upon the member I. The second half of the ellipseis then traced in the same manner as above described with regard to thefirst half.

Adjustment of the fulcrums 3 and 9 is facilitated by the graduations 52upon the member 6 and in order that the said graduations may be equallyuseful whether the stylus is inserted into the opening it or into theopening H, the distance between the two openings is made a unit of thegraduations 52, in the present case, one inch. It is contemplated thatthe opening l'l will be used more commonly and the opening IE only forlarger ellipses.

While I have herein described and shown a preferred embodiment of myinvention, it will be readily understood by those skilled in the artthat the same may be modified in various ways to meet any particular orpeculiar requirement, without departing from the spirit or" myinvention. For example, instead of the rubber band I3, I may employ aspring or other resilient memoer of metal. Similarly, in place of thestuds 3 for holding the parts together, I may employ any well known formof cement for this purpose.

Having thus described my said invention, what I claim and desire tosecure by Letters Patent of the United States is:

1. An ellipsograph comprising a base plate having a rectilinear guidingsurface along one edge, a cover plate arranged in parallel spacedrelation with saidbase plate and having a slot extending from themid-point of said guiding surface and at right angles thereto, a slidingmember within said slot having a bearing in one end, a scribercarryingmember positioned between said base plate and said cover having a slottherein and an opening in alignment with said slot adapted to receive ascriber, a fulcrum pin journaled in said bearing and provided with meansfor clamping it adjustably in the slot of said scriber-carrying member,a second fulcrum pin adapted to be clamped adjustably in saidlast-mentioned slot and having a downward extension for engaging theguiding edge of the base plate, and means for maintaining said extensionin contact with said guiding edge.

2. An ellipsograph comprising a base plate having a rectilinear guidingsurface along one edge, a cover plate arranged in parallel spacedrelation with said base plate and having a slot extending from themid-point of said guiding surface and at right angles thereto, a slidingmember within said slot having a bearing in one end, a scriber-carryingmember positioned between said base plate and said cover having a slottherein, and an opening in alignment with said slot adapted to receive ascriber, said member having a graduated scale thereupon extending alongsaid slot, a fulcrum pin journaled in said bearing and provided withmeans for clamping it adjustably in the slot of said scriber-carryingmember, a second fulcrum pin adapted to be clamped adjustably in saidlast-mentioned slot and having a downward extension for engaging theguiding edge of the base plate, and means for maintaining said extensionin contact with said guiding edge.

3. An ellipsograph comprising a base plate having a rectilinear guidingsurface along one edge, a cover plate arranged in parallel spacedrelation with said base plate and having a slot extending rorn themid-point of said guiding surface and at right angles thereto, a slidingmember within said slot having a bearing in one end, a scribercarryingmember positioned between said base plate and said cover having a slottherein and an opening in alignment with said slot adapted to receive ascriber, a fulcrum pin journaled in said bearing and provided with meansfor clamping it adjustably in the slot of said scriber-carrying member,a second fulcrum pin adapted to be clamped adjustably in saidlast-mentioned slot and having a downward extension for engaging theguiding edge of the base plate, and means for maintaining said extensionin contact with said guiding edge, said means including a band ofresilient material one end of which engages the sliding member while theother end is anchored to the cover plate.

PETER F. DUBOIS.

